Leaves are wilted, stippled, yellowing, and dirty. Leaves may dry out and drop. There may be fine webbing over flower buds, between leaves, or on the lower surfaces of leaves. Plants lose vigor. To check for twospotted spider mites, hold a sheet of white paper underneath an affected leaf and tap the leaf sharply. Minute specks the size of pepper grains will drop to the paper and begin to crawl around.
Apply a horticultural oil or garden insecticide when damage is first seen, following instructions on the label. Mites are difficult to control because they reproduce so rapidly. Repeated applications are necessary, especially during hot, dry weather. Hose down plants with a high-pressure nozzle every few days to knock off webs and mites.